ISHS Acta Horticulturae 740: I International Symposium on Papaya
ACTIVITY OF PAPAYA FRUIT HYDROLASES DURING NATURAL SOFTENING AND MODIFIED SOFTENING |
| Authors: | S. Thumdee, A. Manenoi, R.E. Paull |
| Keywords: | 1-methylcyclopropene, xylanase, galactosidase, pectin methylesterase, glucanase, polygalacturonase |
| Abstract:
Papaya (Carica papaya L.) cultivars show a wide variation in fruit softening, a character that determines fruit quality and shelf life. Fruit softening is thought to be the result of cell wall degradation. The relationship between normal and modified softening and the activity of enzymes related to the degradation of cell wall was studied. ‘Sunset’ papaya fruit were harvested at the color break stage (less than 10% skin yellowing). Fruit were treated with 100 nL L-1 1-methylcyclopropene (MCP) for 12 hours, allowed to ripen at the room temperature and the rate of softening determined. The activity of  -galactosidase, pectin methylesterase (PME) and glucanase were related to fruit softening.
The activity of polygalacturonase (PG) was very low and, its pattern varied and did not relate to the softening pattern.
The activity of endo-xylanase was related to the softening only in the non-MCP-treated fruit but not in the MCP-treated fruit.
The endoxylanase activity of MCP-treated fruit was highly suppressed throughout fruit softening.
The failure of MCP-treated papaya to soften completely and have a rubbery texture may have been caused by a suppression of endoxylanase activity.
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